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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_typetraits.reference.has_trivial_constructor"></a><a class="link" href="has_trivial_constructor.html" title="has_trivial_constructor">has_trivial_constructor</a>
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<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">has_trivial_constructor</span> <span class="special">:</span> <span class="keyword">public</span> <em class="replaceable"><code><a class="link" href="integral_constant.html" title="integral_constant">true_type</a>-or-<a class="link" href="integral_constant.html" title="integral_constant">false_type</a></code></em> <span class="special">{};</span>

<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">has_trivial_default_constructor</span> <span class="special">:</span> <span class="keyword">public</span> <em class="replaceable"><code><a class="link" href="integral_constant.html" title="integral_constant">true_type</a>-or-<a class="link" href="integral_constant.html" title="integral_constant">false_type</a></code></em> <span class="special">{};</span>
</pre>
<p>
        <span class="bold"><strong>Inherits:</strong></span> If T is a (possibly cv-qualified)
        type with a trivial default-constructor then inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>,
        otherwise inherits from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>.
      </p>
<p>
        These two traits are synonyms for each other.
      </p>
<p>
        If a type has a trivial default-constructor then the constructor have no
        effect: calls to the constructor can be safely omitted. Note that using meta-programming
        to omit a call to a single trivial-constructor call is of no benefit whatsoever.
        However, if loops and/or exception handling code can also be omitted, then
        some benefit in terms of code size and speed can be obtained.
      </p>
<p>
        <span class="bold"><strong>Compiler Compatibility:</strong></span> Without some (as
        yet unspecified) help from the compiler, has_trivial_constructor will never
        report that a user-defined class or struct has a trivial constructor; this
        is always safe, if possibly sub-optimal. In addition, in order to correctly
        handle private or deleted default-constructors then C++11's <code class="computeroutput"><span class="identifier">deltype</span></code> is required. Currently (May 2015)
        compilers more recent than Visual C++ 8, GCC-4.3, Greenhills 6.0, Intel-11.0,
        and Codegear have the necessary compiler <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a>
        to ensure that this trait "just works". You may also test to see
        if the necessary <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a>
        are available by checking to see if the macro <code class="computeroutput"><span class="identifier">BOOST_HAS_TRIVIAL_CONSTRUCTOR</span></code>
        is defined.
      </p>
<p>
        <span class="bold"><strong>C++ Standard Reference:</strong></span> 12.1p6.
      </p>
<p>
        <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
        <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">has_trivial_constructor</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
        or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
      </p>
<p>
        <span class="bold"><strong>Examples:</strong></span>
      </p>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">has_trivial_constructor</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span></code> inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
        </p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">has_trivial_constructor</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">*&gt;::</span><span class="identifier">type</span></code>
          is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
        </p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">has_trivial_constructor</span><span class="special">&lt;</span><span class="keyword">int</span> <span class="special">(*)(</span><span class="keyword">long</span><span class="special">)&gt;::</span><span class="identifier">value</span></code>
          is an integral constant expression that evaluates to <span class="emphasis"><em>true</em></span>.
        </p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">has_trivial_constructor</span><span class="special">&lt;</span><span class="identifier">MyClass</span><span class="special">&gt;::</span><span class="identifier">value</span></code>
          is an integral constant expression that evaluates to <span class="emphasis"><em>false</em></span>.
        </p></blockquote></div>
<div class="blockquote"><blockquote class="blockquote"><p>
          <code class="computeroutput"><span class="identifier">has_trivial_constructor</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code>
          is the type <code class="computeroutput"><span class="keyword">bool</span></code>.
        </p></blockquote></div>
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